1. Field of the Invention
The present invention relates to an anthracene derivative, and a light-emitting element, a light-emitting device, and an electronic device each using the anthracene derivative.
2. Description of the Related Art
In comparison with inorganic compounds, organic compounds can have various structures. By appropriate molecular design of organic compounds, materials having various functions can be synthesized. Owing to these advantages, photo electronics and electronics, which employ functional organic materials, have been attracting attention in recent years.
A solar cell, a light-emitting element, an organic transistor, and the like can be given as typical examples of an electronic device using an organic compound as a functional material. Such devices take advantage of electrical properties and optical properties of the organic compound. Among them, in particular, a light-emitting element has been making remarkable progress.
It is considered that a light emission mechanism of a light-emitting element is as follows: when a voltage is applied between a pair of electrodes which interpose a light-emitting layer, electrons injected from a cathode and holes injected from an anode are recombined in the light-emitting layer to form a molecular exciton, and when the molecular exciton relaxes to the ground state, energy is released and light is generated. As excited states, a singlet excited state and a triplet excited state are known, and light emission is considered to be possible through either of these excited states.
In improving the performance of such a light-emitting element, there are many problems which depend on the material, and in order to solve such problems, improvement of the element structure and development of materials have been carried out.
For example, in Reference 1 (United States Patent Application Laid-Open No. 2005/0260442), an anthracene derivative exhibiting green light emission is disclosed. However, in Reference 1, only the PL spectrum of the anthracene derivative is described, and the device performance when the anthracene derivative is applied to a light-emitting element is not disclosed.
Also, in Reference 2 (Japanese Published Patent Application No. 2004-91334), a light-emitting element using an anthracene derivative as a charge transporting layer is mentioned. However, in Reference 2, there is no description on the lifetime of the light-emitting element.
If commercialization of light-emitting elements is considered, extending the lifetime is an important issue. Further, the development of light-emitting elements with much higher performances is desired.